Improvement in speaking-tubes



A. RAN KIN.

Speaking-Tubes.

Patented July 1; 1873.

JYIELE.

AM PHOTOiITMDGRAPH/c ca Mnossamsmacaw.)

UNITED STATES PATENT QFFICE.

ANDREW RANKIN, OF PHILADELPHIA, PENNSYLVANIA.

IMPROVEMENT IN SPEAKING-TUBES.

Specification forming part of Letters Patent No. 140,539, dated July 1, 1873; application filed February 27, 1873.

hinged to the case A, is preferably of castiron, and is concave or recessed at the inner or rear side where there are two annular shoulders or hearings, on w, for disks m a of thin metal, the former being cup-shaped, and both having central openings on a line with the central opening q of the lid.

The disks are of such a size that, when pressed to their seats, they will be retained, by friction against the ledges of the lid, in their places-the trouble and expense of first making independent whistles and then securing them to the lid being avoided, as the disks and lid together constitute the whistle.

I clain1 The combination, in aniouth-piece for speaking-tubes, of the recessed lid B, its shoulders .00 02, opening q, and the perforated plates m n, all constructed and arranged as set forth.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

ANDREW RANKIN. lVitnesses:

WM. A. STEEL, HUBERT HoWsoN. 

